The present invention relates generally to a method and apparatus for rebuilding teeth, and more specifically to a novel retention pin and a method for using it.
In the dentistry field it is, of course, common to rebuild a portion of a tooth. When the tooth portion being rebuild cannot be shaped such that the tooth itself will hold a filling or other artificial tooth portion, then it becomes necessary to use some other method and apparatus for attaching such artificial tooth portion to such tooth. One method in common usage is the use of a retention pin. In using such a retention pin, normally the portion of the tooth which needs to be replaced is ground off down to the dentin portion. Then a very small hole is bored into the dentin portion of the tooth. A small retention pin having threads around the periphery thereof is then either manually or mechanically rotated such that it is screwed down into the hole in the dentin. A portion of such retention pin would then extend outwardly from the dentin portion and would also have threads thereon for facilitating anchoring of an artificial tooth portion thereto. The artificial tooth portion would then be formed over and around such retention pin so that when this artificial tooth portion hardened, it would be secured to the dentin portion of the tooth by the retention pin.
While this has been a generally well accepted procedure, it has been discovered that this procedure causes crazing of the dentin at the point at which the pin connects to the dentin portion of the tooth. In an article beginning on page 941 of J Dent Res in the July-August 1974 issue, vol. 53, no. 4, by Chan et al., the problem was researched and discussed with a conclusion that the wedging of such self-threading retention pins causes these cracks in the dentin portion, thereby eventually causing the connection to fail or deterioration of the tooth to occur.
In the dentistry field, it is also well known to attach tooth portions together by the use of some sort of retention structure, such as a pin which has one portion cemented to a tooth and the other portion having an artificial section which is formed around such retention member. One patent, U.S. Pat. No. 2,721,387 issued to Ashuckian, shows a very complicated structure for attaching an artificial tooth to a person's jaw and having a plurality of barbs thereon for allowing the jaw portion to grow therearound to make a connection. U.S. Pat. Nos. 756,506 to Kidder, 1,517,500 to Fredericks and 4,139,943 to Dragan are illustrations of the prior art showing barbed pins or the like for connecting tooth portions together. This prior art does not, however, recognize the dentinal crazing problem referred to above and does not provide a structure or method for connecting the dentin portion of a tooth to an artificial portion.
One solution to the above identified problem is disclosed in copending U.S. Patent application Ser. No. 82,441, now U.S. Pat. No. 4,259,076 issued Mar. 31, 1981, to Yanney, which is incorporated herein by reference. The present invention is an improvement over this invention.